The present invention relates to an improved mechanism for suppressing bound of swingable elements on a key musical instrument, and more particularly relates to an improvement in a mechanism for suppressing bound of swingable elements such as keys and hammers on a piano.
A piano includes lots of swingable elements each of which swings, on key depression, about a given pivot and returns, on removal of the key depression, to its initial rest position at which a shock absorvable seat is usually provided in order to minimize undesirable bound of the swingable element.
A hammer of a piano is one example.
In construction of a hammer assembly, a hammer is pivoted via a butt to a butt flange and usually rests at an initial position on a hammer rail cloth attached to a hammer rail. When an associated key is depressed, the hammer swings upwards about the butt flange in order to beat a corresponding string. After beating the string, the hammer returns towards its initial rest position on the hammer rail cloth due to repulsion of the string. The quicker the returning motion, the larger the bound of the hammer on arrival at the hammer rail cloth and the hammer cannot swiftly assume its initial rest position on the hammer rail cloth. In other words, such bound on the hammer rail cloth causes belated settlement of the hammer to its initial rest position. When a same key is separatedly depressed at quick tempo during performance, such belated settlement to the initial rest position disenables correct transmission of key motion to the hammer and, as a consequence, string beating cannot be carried out as intended by the player.
A hammer assembly is closely related in motion to an associated key assembly and a hammer hits a jack. Shock caused by this hit is transmitted to the associated key via a wippen and a capstan. During swing motion of the hammer, the key is in a free state with respect to the action assembly. When the shock is transmitted, the key in this free state tends to bound.
Further, bound of a hammer causes vibration of the hammer which seriously delays return motion of the action assembly to its initial rest position, thereby posing ill influence on key touch. Delay in return motion of the action assembly naturally causes corresponding delay in motion of the damper assembly which results in ill damping motion. From these points of view, quick settlement of the initial position by a hammer plays a very important role in performance of a piano. In addition, since a hammer usually has large dynamic energy, its uncontrolled motion tends to cause irregular vibration of related assemblies.
It is already proposed, for example in Japanese Patent Opening Nos. Sho 52-96522 and Sho 58-186797, to arrange a mechanism for absorving dynamic energy of a hammer when it returns towards the initial rest position. Such prior mechanisms, however, are all based on use of a spring or springs which cannot full suppress bound of a hammer at arrival at the initial rest position. When a hammer hits such a mechanism, a spring may once absorve the shock by its elastic deformation. Soon after, however, elastic recovery of the spring acts to push back the hammer. The stronger the shock, the larger the elastic recovery. So, when an associated key is depressed strongly, the elastic recovery causes delay in settlement to the initial rest position by the hammer.
A key of a piano is another example. In construction of a key board assembly, a key is pivoted at its middle to a balance rail and its rear end usually rests at an initial rest position on a back rail cloth attached to a back rail. When the key is depressed, its rear end swings upwards about the balance rail in order to toss up an associated wippen assembly. On removal of depression on the key, its rear end returns towards its initial rest position on the back rail cloth which more or less alleviates shock and noise caused by return of the key end. The softer the back rail cloth, the greater the alleviation. Too soft construction of the back rail cloth, however, is too susceptible to change in environmental conditions and, as a consequence, easy change in dimension. Such change in dimension causes uneven mobil ambit of the key. In order to obviate such a trouble, the back rail cloth is required to have some extent of hardness which disenables ideal absorption of shock and noise when hit by the key end. As a consequence, the key bounds when its rear end hits the back rail cloth and such bound of the key inevitably transmits noize and vibration to the key bed, thereby degrading performance. Such bound also transmit vibration to player's fingers and causes ill influence on key touch, poor damping and difficulty in quickly repeated depression of a same key in performance.
In order to avoid this inconveniency. Japanese Utility Model Publication No. Sho 59-24076 proposes to use felt or the like for absorption shock by the key end. But the materials proposed by this prior proposal are all vulnerable to change in environmental conditions and allow easy change in dimension of the back rail cloth. No constant mobile ambit of the key is assured.